Two recent studies lay out compelling scenarios under which virtually all of the world’s energy needs could be met with renewable energy sources by 2050. But despite their similar end goals, the energy futures foreseen in these two reports—published by the World Wildlife Fund (WWF) and a team of university scientists, respectively—are vastly different.

A wind turbine in South Africa. Will there be more of them in 2050?

WWF’s The Energy Report, published last week in collaboration with Ecofys, a Dutch think tank specializing in renewable energy, concludes that it is technologically and economically feasible for 95 percent of all energy to come from renewable sources by 2050. The authors argue that such a transformation would even be cheaper than relying on conventional, carbon-intense energy sources.

Meanwhile, Mark Z. Jacobson from Stanford University and Mark A. Delucchi from the University of California at Davis have written an ambitious two-part paper titled “Providing all global energy with wind, water, and solar power,” soon be published in Energy Policy. The study concludes that the electrification of all energy sectors can lead to a fully renewable energy supply by as early as 2030, or—if political and social obstacles are taken into account—by 2050.